1. Field of the Invention
The invention relates in general to a touch sensing technique, and more particularly, to a technique capable of reducing a quantity of sensors implemented in a touch sensing device.
2. Description of the Related Art
Operating interfaces of modern electronic products have become increasingly user-friendly and intuitive as technology continues to advance. For example, through a touch screen, a user can directly operate programs as well as input messages/text/patterns, etc. with his fingers or a touch control pen, thus eliminating complications associated with input devices such as a keyboard or buttons. In practice, a touch screen usually comprises a touch sensing panel and a display disposed at the back of the touch sensing panel. According to a position of a touch point on the touch sensing panel and a currently displayed image on the display, an electronic device determines an intention of the touch to execute corresponding operations.
Existing touch sensing techniques can be categorized into resistive, capacitive, electromagnetic, ultrasonic and optic types. For a mutual-capacitive touch sensing technique, for example, a plurality of transparent sensing wires, arranged in a matrix, are disposed on the back of a touch sensing panel, as shown in FIG. 1. In this example, the sensing wires in the X direction are driving sensing wires whereas the sensing wires in the Y direction are receiving sensing wires. Still with reference to FIG. 1, each of the driving sensing wires is connected to a driver 12, and each of the receiving sensing wires is connected to a receiver 14. Generally, the drivers 12 sequentially send driving signals, and the receivers 14 continuously receive sensing signals. When a valid touch takes place, capacitance coupling occurs between the driving sensing wire and the receiving sensing wire corresponding to the touch point, resulting in a change in a sensing signal associated with a mutual capacitance. According to the receiver 14 which detects the change in the sensing signal and the driver 12 which sent out the driving signal at the time of the touch, a subsequent circuit determines a coordinate of the touch point with respect to the X and Y directions.
The number of drivers 12 and receivers 14 are closely related to a size of the touch screen. Consider a situation where a gap between every two sensing wires in the X direction and in the Y direction is 5 mm. Supposing a number of the drivers 12 is D and a number of the receivers 14 is R, a sensing region correspondingly has a maximum length of R*5 mm and a maximum width of D*5 mm. In other words, the number of drivers 12 and receivers 14 increases as the size of the touch screen gets larger, and consequently inevitably increases hardware costs. As with the mutual capacitive touch screen, other types of touch screens are also faced with the same issue.